The invention relates to a leno device for weaving machines, preferably double rapier weaving machines for plain velvet or carpets, designed to obtain non-fraying edges.
Leno devices are used in a weaving loom in order to position a part of the warp ends, the so-called leno threads, first to the right and then to the left of the standing threads such that the leno threads are wound or slung around the standing threads.
The device required to execute this operation is rather complicated, and various attempts have already been made to simplify it.
Among these, a solution was specified in German Gebrauchmuster No. 80 05 822 published on July 7, 1980, whereby on one hand the standing threads are positioned by means of needles and on the other hand the leno threads are positioned by the respective movements of healds fitted with eyes and of a guide plate fitted with inclined slots through which the leno threads are guided. This leno device requires three shed motions with their associated weaving frames, namely a weaving frame with 1/1 movement for the needle bar, a weaving frame with 1/1 movement for the slot bar and a weaving frame with 2/2 movement for the leno thread positioning eyes.
Naturally, this is in itself not a simple drive, which requires three elements of the existing shed motion installation, such as a dobby mechanism or a cam mechanism. Furthermore, leno device cannot be separately timed with respect to the main shaft.
U.S. Pat. No. 3,369,570 shows a leno salvage device that includes a carrier with vertically spaced needle blocks equipped with vertically opposed needles and friction rods. Also, a leno bar is slideably received in a slot extending through the leno bar. This disclosure concerns a device associated with and dependent on a particular weaving frame and suffers from the aforementioned disadvantages in that it does not have a simple drive, cannot be separately timed with respect to the main shaft and cannot be practised in double rapier machines without difficulties.